1. Field of the Invention
The present invention relates to an image-signal processing apparatus well functioning as a recording/reproduction apparatus for recording typically a video signal onto a recording medium and reproducing the video signal from the recording medium, an image-signal processing method adopted by the image-signal processing apparatus and an image-signal processing computer program implementing the image-signal processing method.
2. Description of the Related Art
In many of the existing digital-signal processes carried out on a base band video signal, the digital signal is a quantized signal having a quantization bit count of eight. For this reason, a large number of video contents are produced and recorded as data of eight bits and, in addition, most of display units each used for displaying a video content are eight-bit oriented display units.
By the way, when a digital signal obtained as a result of an eight-bit quantization process is displayed on a display unit as a video, the display process raises a problem that pseudo contours appear inevitably at locations at which the luminance value should change gradually. By a pseudo contour, a stripe having the shape of a contour is meant. This is because, in some cases, the width of an eight-bit quantization process is coarse so that gradual luminance changes are unavoidably observed as stair-step changes.
In order to avoid such image deteriorations, there has been provided a technique whereby an image signal having precision not exceeding the quantization precision is reproduced by increasing the bit count of a digital signal obtained as a result an eight-bit quantization process to a larger number such as ten or 12.
Patent Document 1 (Japanese Patent Laid-open No. Hei 9-219833) discloses a technique for generating a digital signal having a bit count greater than the input digital signal.